1. Field of the Invention
The present invention generally relates to a wireless communication system, and more particularly to a method and system for allocating uplink and downlink data bursts in a wireless communication system.
2. Description of the Related Art
Extensive research is being conducted on fourth-generation (4G) communication systems serving as next generation communication systems that provide users with services based on various qualities of service (QoS) at a transmission rate of about 100 Mbps. In the current 4G communication system, extensive research is being conducted to ensure mobility and QoS and support high-speed services for broadband wireless access (BWA) communication systems such as a wireless local area network (LAN) system and a wireless metropolitan area network (MAN) system. A typical communication system is based on the Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system standard.
The IEEE 802.16 communication system is a BWA communication system using orthogonal frequency division multiplexing/orthogonal frequency division multiple access (OFDM/OFDMA). As compared with the conventional wireless technology for a voice service, the IEEE 802.16 communication system can transmit a large amount of data in a short time using a wide data bandwidth and can efficiently use a channel because the users can share a common channel. In the IEEE 802.16 communication system, all users associated with a base station (BS) share a common channel. Since the BS allocates an interval in which each user uses a channel for each uplink (UL) or downlink (DL) frame, the BS notifies the mobile stations of UL and DL access information so that the users can share the common channel. UL and DL MAP messages are used to supply the notification of the UL and DL access information.
A hybrid automatic repeat request (H-ARQ) MAP message is a type of MAP message used to support a mobile station (MS) available in an H-ARQ scheme. For example, the MS interprets an H-ARQ MAP message when receiving the message from the BS. A MAP information element (IE) included in the H-ARQ MAP message is referred to as a compact UL/DL_MAP IE. The MS can receive or transmit a data burst according to information of Compact UL/DL-MAP_IE.
FIG. 1 illustrates a frame structure used in a conventional wireless communication system.
Referring to FIG. 1, a frame can be divided into a DL subframe and a UL subframe.
The DL subframe includes a preamble transmission interval 10, a MAP transmission interval 20 and a data transmission interval 30.
The MAP transmission interval 20 includes a frame control header (FCH) 21 for transmitting information for decoding and demodulating MAP information and H-ARQ MAP1 22 and H-ARQ MAP2 23 for transmitting information to a desired MS. The data transmission interval 30 includes allocated data bursts to be transmitted to the MS using a plurality of subchannels in a specific symbol interval. Here, the data bursts are sequentially allocated in a subchannel unit of a vertical axis during a unit symbol interval of a horizontal axis. When data burst allocation is completed for all subchannels of one symbol interval, data bursts are sequentially allocated in the subchannel unit during the next symbol interval.
That is, Data Bursts 1, 2 and 3 of FIG. 1 are allocated in a specific symbol interval ‘n’. For example, if Subchannels 0 to 5 are completely allocated for Data Burst 1, the BS allocates Data Burst 2 to Subchannels 6 to 8 and then allocates Data Burst 3 to Subchannels 9 to 10.
When the data burst allocation is completed in the ‘n’ symbol interval, the BS sequentially allocates Data Bursts 4 and 5 to subchannels in the next symbol interval, i.e., the ‘n+1’ symbol interval. The data burst allocation method as described above is referred to as “one-dimensional data burst allocation”.
Next, the UL subframe will be described. The UL subframe includes a control information transmission interval 40 and a data transmission interval 50.
Data bursts for UL signal transmissions of MSs are allocated in one dimension in the data transmission interval 50 of the UL subframe as in the data transmission interval 30 of the DL subframe. That is, the end time of a previous data burst corresponds to the start time of the next allocated data burst.
When the BS (or higher-level stage) allocates data bursts in one dimension as described above, MAP overhead can be minimized. However, it is difficult for a specific data burst to be applied to a modulation and coding scheme. In other words, the modulation and coding scheme is applied in a symbol interval unit. The modulation and coding scheme cannot be applied when a specific data burst is allocated during two symbol intervals.
When the BS and a neighbor BS operate in an identical subchannel band, interference between the BSs results in data burst loss. Accordingly, data transmission efficiency is degraded.